If you run magless, then properly true tires are the best thing you can do to ANY car to improve performance, regardless of the track they run on. Cars that chatter and hop will run smooth as silk on perfectly round tires. As someone said long ago, sanding tires on paper or whatever on the car just gives you a smoother egg. That's not truing. It DOES improve things a bit, and can get them pretty close to true. But like I said, if you run magless, the difference made by perfectly true tires can be astonishing.
Or, you can just replace all your wheels with metal ones. Of course then you're usually having to change the axle. Once you change the axle you're often changing the gears. If you're lucky you might not have to change the pinion. And let's not forget the new tires to properly fit the new wheels. So, you've just dropped $40 on parts for a car. It should certainly run better after that, but if you'd rather have that money to put toward new cars or other items, then a tire truer will save you money in the long run.
Hudys and similar (ScaleAuto, and a couple others) are great... for metal wheels. If all you run are slot.it and NSR, and other high-end cars that come with metal wheels, then by all means get one of those and true one wheel at a time. If you have some Scalextric (and many other brands) in your collection, with plastic press-on wheels, then the Hudy will do you no good. You need a whole axle machine, such as the Area 3 Tyre True, or the Tire Razor. With these units, you pop the whole axle out of your car, set it up on the truer, and true down both tires at once without having to remove them from the axle. Rather than spending $20-40 per car to "fix" wobbly plastic wheels, spend $150 (Tire Razor price) just once, and true every car in your collection, whether it has metal or plastic wheels. If you do the math, for most people, it's a no-brainer.
But, if you run magnet cars only, it doesn't really matter that much. Sure true tires help magnet cars, but the difference is much smaller. You might not even realize anything is wrong while the magnet is still in.
I own a Tire Razor, and I love it. I would give up my slot.it and NSR cars before I would give up my Tire Razor, and that's not an exaggeration. Amateur home racers can appreciate smooth running cars as much as competitive club racers can. That "True and Clean" machine is an expensive replacement for the track and controller you already own (and probably have spares of you can dedicate to this purpose anyway). But hey, there's one born every minute.